1. Field of the Invention
This invention relates generally to semiconductor integrated circuit packages, and more particularly to methods and apparatus pertaining to the manufacture of flex tape ball grid array packages.
2. Description of the Related Art
Tape ball grid array packages (TBGA""s) are an increasingly common form of packaging for integrated circuits. TBGA""s comprise a flexible plastic tape comprising a dielectric material, such as Kapton, and a metal pattern (traces) formed on the dielectric material. The metal pattern is connected to bond pads on an integrated circuit. Each of the traces is connected to a solder ball, which serves as the electrical interface between the package and a printed circuit board. In this manner, integrated circuit bond pads in TBGA""s are electrically coupled to an appropriate solder ball.
The flexible tape material is relatively thin and therefore allows the entire package to be correspondingly thin and lightweight. These characteristics are beneficial for systems that are portable, such as cellular phones and other handheld electronic devices.
During the assembly of TBG""s, due to the thin nature of the flexible tape, the tape must be supported while a die is attached to it. One conventional support structure for a flexable tape comprises, as shown in FIG. 1a, a metal sheet 10 with openings 12 therein, including opening 12a. The metal sheet 10 has sprocket holes such as hole 8 that allow it to moved along during the assembly process. For ease of description, the packaging of die will be described will be appreciated that the same process is applied to assembly a plurality of packages, one for each of the openings 12.
As shown in FIG. 1b, a flexible tape substrate 14 with a top side 13 (see FIG. 1c), to which a die will be attached, and a bottom side 15, to which solder balls will be attached, is attached to the metal sheet 10. Specifically, an adhesive is applied to the metal around the periphery of the opening 12a and the periphery of the top side 13 is attached to the adhesive. The flexible tape substrate 14 is larger than the opening 12a such that, as shown by dotted line in FIG. 1c, the periphery of the top side 13 is covered by the metal sheet 10 when viewed from the top side 13.
As shown in FIG. 1d, a die 17 is attached to the top side 13 and wire bonds connect bond pads on the die 17 to traces on the top side 13. After connecting the die to the top side 13 of the tape, and the flexible tape substrate 14. Solder balls are then attached to the bottom side 15, of the flexible tape, which also involves heating the metal sheet 10 and the flexible tape substrate 14. Finally, the flexible tape substrate 14 is removed from the support by scribing around the molding to create an individual package.
The metal sheet 10 has different thermal expansion characteristics in comparison with the flexible tape substrate 14. This mismatch causes the flexible tape substrate 14 to warp or stretch when the flexible tape substrate 14 and metal sheet 10 are heated together, which occurs during molding and solder ball attach, as described above. Warping and/or stretching of the flexible tape substrate 14 can damage the fine metal traces on the flexible tape substrate 14 and can cause the resulting package to be warped.
It would be desirable to decrease the warping or stretching of a flexible tape substrate.
The present invention decreases the warping or stretching of a flexible tape substrate. According to the present invention, a method for creating a package for a semiconductor die, the package comprising a flexible tape, comprises the following steps. A support with an opening has a plurality of arms extending through at a portion of the opening. For example, for a square opening, there may be eight arms, two extending from each side of the opening. The arms preferably form a xe2x80x9czxe2x80x9d shape or some other shape with a transverse component.
The flexible tape is then attached to the ends of the arms within the opening such that the flexible tape is supported by the arms. A die is attached to the flexible tape, the die is preferably covered with a molding compound, and the die/flexible tape assembly is scribed from the support, thereby creating an individual package.